Conventional apparatuses for dissolving and mixing a gas and a liquid include those having a suction device which is a fluid channel having a restriction portion to absorb a gas into a liquid in order to form a mixed flow of the gas and liquid, as disclosed in Japanese unexamined patent publication No. H6-285345 of the applicant. Such a suction device includes an expanded portion formed by a pipe line that is gradually expanded downstream of the restriction portion and includes a gas intake channel for introducing a gas provided thereon slightly downstream of the restriction portion. A liquid is delivered by a pressure to the suction device. The flow of the liquid delivered by a pressure forms a negative pressure at the restriction portion to suck the gas, thereby forming a mixed flow of the gas and liquid.
In the case of the apparatus for mixing a gas and a liquid disclosed in the above-mentioned patent publication, the pressure to deliver a liquid becomes high, because it operated by supplying a gas into the liquid by utilizing the energy of the liquid delivered by a pressure, i.e., a negative pressure produced by the rate of the flow. This has resulted in a problem in that the pump as a means for pressure delivery is expensive and there is a poor choice for the pump because it consumes high motive power and must provide a high pumping pressure.
The present invention has been conceived taking the above-described problem with the prior art, and it is an object of the invention to provide a method and an apparatus for dissolving and mixing a gas and a liquid which allow a gas and a liquid to react and to be dissolved efficiently with less energy.